1. Field of the Invention
The present invention relates to a small electronic apparatus such as a scientific calculator capable of performing input and display of a mathematical expression in textbook format.
2. Description of the Related Art
As prior art, there has been known Japanese Unexamined Patent Publications JP-A 4-252351 (1992), JP-A 5-35685 (1993), JP-A 6-202989 (1994) and so on.
First, JP-A 4-252351 discloses input of an expression in textbook format. Further, JP-A 5-35685 discloses input and edit in textbook format, particularly in respect of a fraction. Further, JP-A 6-202989 discloses input and editing of an expression in simplified textbook format.
According to the prior art, as described in the above-mentioned publications, in a small electronic apparatus, when a mathematical expression is input and displayed in textbook format, the object of the input and display is only one mathematical expression, and a plurality of mathematical expressions inputted cannot be displayed within the same screen at the same time.
Further, when such a mathematical expression as shown in FIG. 9A is displayed in textbook format, the outline of the expression can be easily understood at a glance as shown by a screen 50a of FIG. 9B. However, since a display is performed in a horizontal line, when such a mathematical expression as shown in FIG. 10A is displayed in textbook format in a small electronic apparatus having a display unit whose screen has a small lateral width, a long mathematical expression cannot be displayed within a screen 51a as shown in FIG. 10B, and the whole of the expression cannot be seen unless a screen 51b is displayed by scrolling the screen 51a as shown in FIG. 10C.
Meanwhile, in one line format, even in the case of a long expression, the whole of the expression can be seen as shown by a screen 51c in FIG. 10D, but there is a disadvantage in that when the expression is complicated, the outline of the expression is difficult to understand as shown by a screen 50b in FIG. 9C.
Further, in the prior art, it is impossible to input and edit mathematical expressions within the same screen in a state that these two different formats coexist.
In the prior art, a plurality of mathematical expressions can be inputted and displayed within the same screen only in one line format, and on the other hand, only every one expression can be inputted and displayed within the same screen in textbook format.
Hence, the invention makes it possible to input and display a plurality of mathematical expressions within the same screen in textbook format.
Further, in the prior art, in order to display mathematical expressions within the same screen, only one or the other of textbook format and one line format can be selected, and it is impossible to have both formats to coexist.
Hence, in order to utilize both characteristics that the outline of a mathematical expression is easy to understand in textbook format and that the whole of a mathematical expression can be seen at a glance in one line format, the invention causes both formats to coexist, so that a plurality of mathematical expressions are inputted and displayed.